David Lammy, the higher education minister, said he was "very worried about the days that will follow" while Peter Hain, the Welsh Secretary, said black, Jewish and Muslim people will now "sleep much less easily".

But members of the three main parties who agreed to appear on the panel alongside Mr Griffin said that his appearance had left him "exposed".

Mr Lammy, who was one of Britain's first black Government ministers, said ordinary people from ethnic minority backgrounds could face violence as a result.

"Many people across the country, black and white, will be appalled that Nick Griffin has been given a platform on the BBC's flagship current affairs programme for his terrible racist views.

"Many others, a long way from Broadcasting House, will be left very scared."

Mr Hain, who made a last-ditch appeal to the BBC to drop the BNP leader, said: "The BBC should be ashamed of single-handedly doing a racist, fascist party the biggest favour in its grubby history.

"Our black, Muslim and Jewish citizens will sleep much less easily now the BBC has legitimised the BNP by treating its racist poison as the views of just another mainstream political party when it is so uniquely evil and dangerous."

But Jack Straw, the Justice Secretary, who appeared alongside Mr Griffin on the panel, said: "For the first time the views of the BNP have been properly scrutinised."

Lady Warsi, the Tory shadow minister for community cohesion, who also appeared, said: "When he was questioned on his views his face of extremism was exposed."

Despite a hostile reaction from the audience, Mr Griffin claimed that it had helped him win over "millions" of people.

"A huge swath of British people will remember some of the things I said and say to themselves they've never heard anyone on Question Time say that before and millions of people will think that man speaks what I feel," he said afterwards.

"I think people will see the extraordinary hostility shown to me from the people representing the three old parties."

He added: "They put us on in London where the indigenous population is in the minority so we don't have much sympathy or support."